Abstract: An AM stereophonic demodulator circuit for an amplitude/angle modulation system, comprising an AM detector circuit for producing a stereophonic sum signal (L+R), an FM or PM detector circuit for producing a stereophonic difference signal (L-R), and control means for extracting a DC voltage proportional to an antenna input level from the AM detector circuit so as to use the DC voltage to control the gain and amplitude of an FM or PM detector stage including the FM or PM detector circuit.

Abstract: A local oscillation circuit for a tuner having a reduced inter-channel deviation in AFC sensitivity. The local oscillation circuit comprises a resonance circuit capable of varying a tuning frequency by means of a variable capacitive element additionally provided with a variable capacitive diode which is applied with a control voltage in dependence upon variation in the frequency detected from the output signal of the tuner, thereby to effect an automatic frequency control. A single variable capacitive diode is coupled to the variable capacitive element of the resonance circuit in a parallel and a series connections.